The Equation Group is known to use some of the most advanced malware and probably helped develop the infamous Stuxnet computer worm, according to security firm Kaspersky Lab.

Over the weekend, hackers known as the Shadow Brokers claimed to have stolen the very cyber weapons the group has used.

“We auction best files to highest bidder. Auction files better than Stuxnet,” the hackers said in a Tumblr posting using broken English.

Samples of the stolen files are dated most recently to 2013, and they do contain coding related to hacking, said Nicholas Weaver, a security researcher at the International Computer Science Institute in California.

“It appears to be a large amount of NSA infrastructure for controlling routers and firewalls, including implants, exploits, and other tools,” he said in an email.

Although the exploits were poorly coded, “nonetheless, this appears to be legitimate code,” he added.

Virginia-based Risk Based Security has also looked at the sample files and said that one of the exploits contains an IP address registered by the U.S. Department of Defense.

None of this means that the NSA has been hacked. The Shadow Brokers may have simply come across a compromised system that was hosting the exploits, Risk Based Security said in a blog post.

It's also possible the Shadow Brokers are promoting a big scam. Deception-based schemes are very common in hacking, Risk Based Security added. The NSA hasn't acknowledged any ties with Equation Group and on Monday, it didn't respond for comment.

Nevertheless, the Shadow Brokers are asking buyers to bid with bitcoin, although the group is offering no guarantees it will hold its own end of the bargain.

However, it’s promising to publicly dump all the files for 1 million bitcoins or US$566 million. So far, the group has only received $45 worth in bitcoin, but it's hoping that "wealthy elites" end up trying to buy the stolen files.

In their Tumblr posting, the Shadow Brokers warned that the hacking tools they've stolen could be used on banks to cause havoc.